In an information processing system called a thin client system, a server manages resources, such as application programs and files, and a client terminal has minimum functions to use such resources. Hereinafter, the application programs may simply be described as the “applications”.
In such a thin client system, the client terminal acts as if the client terminal plays a key role in executing processing and holding data while displaying a result of processing executed by the server and data held by the server on a screen of the client terminal.
For example, the server in the thin client system may execute a service application regarding services such as document preparation and e-mail, and display a processing result of the application on the client terminal. It is preferable that, besides such a service application, an application handling high-resolution images, such as computer aided design (CAD), and an application handling videos or moving images, and the like are expanded as the range of application of the thin client system.
As a communication protocol in the thin client system, a Remote Desktop Protocol (RDP), a Remote Frame Buffer (RFB) protocol, and the like are known, for example. The RFB protocol is a protocol used in Virtual Network Computing (VNC) (see, for example, “Welcome to TigerVNC”, [online], [Searched on Jun. 4, 2014], Internet <URL: http://sourceforge.net/apps/mediawiki/tigervnc/index.php?title=Welcome_to_TigerVNC>).
In the case of handling large volumes of data, such as images and videos, using such communication protocols, there is a problem of an impaired response to an operation executed by the client terminal. Such a problem is not limited to the case of handling images and videos but is common to the case where large volumes of data are transmitted between the server and the client terminal during screen update and the like in the thin client system.
Therefore, application of an image compression algorithm with a different compression rate to screen data may optimize a data transfer amount between the server and the client terminal. For example, by using a lossy compression algorithm to compress the screen data, the data transfer amount may be significantly reduced in exchange for reduction in image quality, thereby improving the response to the operation.
There has also been known an information processing apparatus configured to divide an image for displaying an execution result of a computer on a display unit in a terminal apparatus into regions and transmit an image in a frequently changed region by video compression (see, for example, Japanese Laid-open Patent Publication No. 2011-238014).
There has also been known a video real-time distribution system configured to distribute video data in real time from an image coding transmission apparatus to a client terminal through an image server (see, for example, Japanese Laid-open Patent Publication No. 2003-209828). This video real-time distribution system performs disconnection and reconnection between the image server and the client terminal every time the amount of image data held in the image server reaches a certain value or more.